Media sharing in messages in HLD - Architecture Diagram

System Overview - Media sharing in messages

This system allows users to share media files like images, videos, and audio within their messages. It ensures media is uploaded, stored securely, and delivered efficiently alongside text messages.

Key requirements include fast upload/download, media format support, storage scalability, and message synchronization.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +---------------------+
  |                     |
  v                     v
Media Service         Messaging Service
  |                     |
  v                     v
Media Storage         Message Database
  |
  v
CDN Cache

Components

User

client

Initiates media upload and message sending requests

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Routes requests to appropriate backend services and handles authentication

Media Service

service

Handles media upload, processing, and retrieval

Messaging Service

service

Manages message creation, storage, and delivery

Media Storage

storage

Stores media files persistently and securely

Message Database

database

Stores message metadata and text content

CDN Cache

cache

Caches media files close to users for fast delivery

Request Flow - 11 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Media Service

Media Service → Media Storage

Media Service → API Gateway

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Messaging Service

Messaging Service → Message Database

User → CDN Cache

CDN Cache → Media Storage

Failure Scenario

Component Fails:Media Storage

Impact:Media files cannot be stored or retrieved, causing upload failures and broken media links in messages

Mitigation:Use replicated storage clusters with failover; CDN cache serves previously cached media to reduce impact

Architecture Quiz - 3 Questions

Which component handles routing requests to the correct backend service?

A Media Service

B API Gateway

C Load Balancer

D CDN Cache

Design Principle

This design separates media handling from message processing to optimize storage and delivery. Using a CDN cache reduces latency for media retrieval. The API Gateway centralizes routing and security, while the load balancer ensures scalability and availability.

Practice

1. What is the main reason to separate media storage from message text storage in a messaging system?

easy

A. To reduce the number of messages sent

B. To make the user interface more colorful

C. To improve performance and scalability by handling large media files separately

D. To avoid using cloud storage services

Solution

1. Step 1: Understand media file size impact

   Media files like photos and videos are large and can slow down message storage if kept together.

2. Step 2: Separate storage benefits

   Separating media storage allows using specialized systems like CDNs and cloud storage optimized for large files.

3. Final Answer:

   To improve performance and scalability by handling large media files separately -> Option C

4. Quick Check:

   Separate media storage = better performance [OK]

Hint: Separate big files from text for faster message handling [OK]

Common Mistakes:

• Thinking media size doesn't affect performance
• Confusing UI design with storage design
• Ignoring scalability needs

2. Which component is essential for efficiently delivering media files in a messaging system?

easy

A. Content Delivery Network (CDN)

B. Message queue

C. Load balancer for text messages

D. Database index

Solution

1. Step 1: Identify media delivery needs

   Media files are large and need fast delivery to users worldwide.

2. Step 2: Role of CDN

   A CDN caches media files close to users, reducing latency and bandwidth usage.

3. Final Answer:

   Content Delivery Network (CDN) -> Option A

4. Quick Check:

   Fast media delivery = CDN [OK]

Hint: Use CDN to speed up media file delivery [OK]

Common Mistakes:

• Confusing CDN with database indexing
• Thinking load balancers handle media files
• Ignoring network latency

3. Given a messaging system where media files are uploaded to cloud storage and messages store only media URLs, what is the expected behavior when a user sends a photo?

medium

A. The photo is embedded directly in the message text stored in the database

B. The photo is uploaded to cloud storage and the message stores a URL pointing to it

C. The photo is sent as a base64 string inside the message

D. The photo is stored in the message queue before delivery

Solution

1. Step 1: Understand media upload flow

   Media files are large, so they are uploaded separately to cloud storage for efficiency.

2. Step 2: Message stores media reference

   The message contains a URL pointing to the media location, not the media itself.

3. Final Answer:

   The photo is uploaded to cloud storage and the message stores a URL pointing to it -> Option B

4. Quick Check:

   Media URL in message = cloud upload [OK]

Hint: Messages store URLs, not media files directly [OK]

Common Mistakes:

• Embedding large media in message text
• Using base64 which increases size
• Storing media in message queues

4. A messaging system stores media files directly in the message database causing slow queries. What is the best fix?

medium

A. Increase database RAM without changing design

B. Delete all media files from messages

C. Compress media files and keep them in the database

D. Move media files to cloud storage and store only URLs in the database

Solution

1. Step 1: Identify problem with current design

   Storing large media in the database slows down queries and reduces scalability.

2. Step 2: Apply best practice for media storage

   Moving media to cloud storage and storing URLs improves performance and scalability.

3. Final Answer:

   Move media files to cloud storage and store only URLs in the database -> Option D

4. Quick Check:

   Separate media storage = faster queries [OK]

Hint: Store URLs, not media, in message DB for speed [OK]

Common Mistakes:

• Relying only on hardware upgrades
• Compressing media but still storing in DB
• Removing media reduces feature, not fix

5. You design a messaging app that supports sharing photos and videos. To handle millions of users, which combination of components best ensures scalability and fast media delivery?

hard

A. Upload media to cloud storage, use a CDN for delivery, and store media URLs in messages

B. Store media in the message database and use a single server for all requests

C. Send media as base64 in messages and cache messages on client devices

D. Use peer-to-peer media sharing without central storage

Solution

1. Step 1: Analyze scalability needs

   Millions of users require scalable storage and fast delivery without overloading servers.

2. Step 2: Choose best architecture components

   Cloud storage handles large media files reliably; CDN speeds up delivery globally; storing URLs keeps messages lightweight.

3. Step 3: Evaluate other options

   Single server or embedding media causes bottlenecks; peer-to-peer lacks reliability and control.

4. Final Answer:

   Upload media to cloud storage, use a CDN for delivery, and store media URLs in messages -> Option A

5. Quick Check:

   Cloud storage + CDN + URLs = scalable media sharing [OK]

Hint: Combine cloud storage, CDN, and URLs for scalable media [OK]

Common Mistakes:

• Storing media in DB causing bottlenecks
• Sending base64 increases message size
• Ignoring global delivery speed